During the production of semiconductor components such as, by way of example, memory chips, in particular DRAM memories (“dynamic random access memories”), the individual integrated circuits are firstly produced at the wafer level and then singulated into semiconductor chips. After singulation, the functional chips are fitted in suitable housings, contact-connected and encapsulated. Afterward, the encapsulated chips, for producing a memory module, are applied to a module board and soldered thereto. Equally, it is also possible for a plurality of encapsulated or non-encapsulated chips to be soldered on one another. Sometimes, rework soldering steps are additionally carried out on the finished module.
Accordingly, the semiconductor components undergo a multiplicity of temperature-critical process steps on the way from the semiconductor chip to the finished component. Since the temperature-critical process steps during soldering can lead to parameter alterations in the individual semiconductor chips, for example to an alteration of the retention time in the case of DRAM memory chips, the maximum soldering temperature and also the soldering profile are specified precisely. The retention time is that time during which the information stored in a memory cell is retained in recognizable fashion.
In this case, the problem arises, on the one hand, that the temperature loading actually acting on the semiconductor chip cannot be determined exactly. Although the temperature of the soldering tip can be determined, it is not readily possible to demonstrate what temperature the chip itself experiences. Many of the soldering steps after production of the individual semiconductor chip may also be carried out outside the responsibility of the chip manufacturer, for example by subcontractors or by the customer itself.
Overall, it would be desirable, therefore, to be able to determine and store the actual temperatures to which a semiconductor chip has been exposed during the soldering process, and in particular the associated temperature profiles.
U.S. Pat. No. 6,630,754 B1 describes a semiconductor arrangement in which a temperature sensor monitors a chip temperature and instigates a corresponding action when a threshold value is exceeded. During operation of a processor arranged on a circuit board, the operating temperature of said processor is determined and, when a threshold value is exceeded, by way of example a fan is activated or the clock frequency is reduced. The temperature is determined in analog fashion. A temperature signal is subsequently processed further by the processor. Voltage is supplied to the arrangement outside the processor.
In U.S. Pat. No. 5,444,637, the temperature on a semiconductor wafer during wafer processing is determined in order to monitor a fabrication process step. The semiconductor wafer has, inter alia, a processor and a battery and stores respective temperature values in a nonvolatile manner when a temperature threshold value is exceeded.
The stored temperature values can subsequently be read out. Voltage supply and signal processing and also temperature sensor are arranged at a distance from one another on the semiconductor wafer.